Specifically speaking of some dry toner cartridge manufacturers, it is their intent that users of their toner cartridges replace them after initial use. In this regard, the number of cartridges purchased is far in excess of those that would be purchased if they could be maintained or recycled. In fact, a subindustry of toner cartridge recyclers has evolved because of the need to reduce the high costs involved in operating copy machines and digital printers. It is much less expensive to recycle a used cartridge than to replace it with a new one.
The toner cartridge, which contains the photo conductive drum and a toner bin body with a magnetic feed roller device and a corona wire to charge the drum, along with a wiper blade and dust bin to clean the drum and collect the waste, comprises an important part of the copier or printer. It is about seventy percent (70%) of the image-making portion of the machine. In addition, the cartridge has light shutters and a protective door flap for the drum and, in some cases, geared counters to indicated approximate toner level, all of which combine to make this an expensive product for the ultimate consumer.
In operation, toner particles (approximately 10 microns in size) are transferred from the toner bin onto the magnetic feed roller by magnetic attraction; the toner contains iron-like particles which are magnetically attractable. Here they are leveled onto the surface of the feed roller in a thin layer by a doctor blade. The toner becomes charged, by a rubbing action against the doctor blade, as it rotates onto the magnetic feed roller. The magnetic feed roller operates at a bias voltage of several hundred volts, mixed with an alternating ripple voltage providing the impetus for the statically charged toner particles to be transferred from the magnetic feed roller onto the charged photoconductive drum surface, thereby forming an image from the photo-electromagnetic radiation information having been received on the photoconductive drum surface. Toner particles seek the areas on the drum that are of a different intensity of charge, though not necessarily opposite charge. The final print image is produced by transference of toner particles from the photo conductive drum onto a medium of choice resulting in a finished printed product. This is accomplished by the printed medium, or paper, being charged by a corona wire (or other means) in an opposite polarity of the toner particles. The toner thusly lying in place on the print medium is then melted or pressed onto that medium, thereby achieving a permanent print.
Due to factory construction and design of certain dry ink processing cartridges used in copy machines and digital printers, toner dust enters into an area of critical electrical connection at the bias voltage rotating connection of the magnetic roller. This accumulated toner, mixed with oxidized metal particles from the contacts, disrupts continuity of electrical connection.
Subsequent to repeated use of the toner cartridge, the aforementioned toner particles and oxidized metal particles accumulate within the critical point of electrical connection thus inhibiting a smooth transference of toner from the feed roller onto the photoconductive drum. This problem is exacerbated by a factory produced, thin film of lubricant at the point of rotating electrical connection of the magnetic feed roller, thereby causing the particles to adhere to the lubricant and remain in the contact area.
When the foreign particles accumulate in this area of electrical connection, minute variations of bias voltage result which affects the transference of the toner onto the photoconductive drum. This is especially noticeable where graphics having large black images are used, or where half-toned dots are involved. If the cartridge is recycled at this point, it is typically disassembled and cleaned to remove the foreign particles from the electrical contact area. Additionally, the lubricant is usually wiped away to prevent further coagulation of new particles in that area. However, it is cumbersome and time consuming to disassemble the bias electrical connection and clean the contacts.